Process of dimerizing acrylonitrile

ABSTRACT

ACRYLONITRILE CAN BE EFFICIENTLY DIMERIZED BY HYDROGEN IN THE PRESENCE OF A CATALYST FORMED BY THE REACTION OF SOLUBLE RUTHENIUM COMPOUNDS WITH SALTS OF WEAK ACIDS AND ADSORBED ON CHARCOAL OR N ALUMINA. THE SELECTED SUPPORTS ENHANCE THE YIELD OBTAINED.

United States Patent M 6 Claims AllSTRACT OF THE DISCLOSUREAcrylonitrile'can be efliciently dimerized by hydrogen in the presenceof a catalyst formed by the reaction of soluble ruthenium compounds withsalts of weak acids and adsorbed on charcoal or a alumina. The selectedsupports enhance the yield obtained.

RELATED APPLICATION This application is a division of our copendingapplication S.N. 654,329 filed July 19, 1967, now US. 3,562,- 181.

FIELD OF THE INVENTION The invention relates to a process for thepreparation of dinitriles from acrylonitrile.

BACKGROUND OF THE INVENTION Heretofore adiponitrile, which is anintermediate in the production of some polyamides, has been a relativelyhigh cost chemical, since the commercial manufacture requires a seriesof steps employing poisonous gases or the use of electric power.Recently it has been discovered that ruthenium metal and salts thereofeffective catalysts for the preparation of adiponitrile and itsprecursor 1,4-dicyanol-butene by the dimerization of acrylonitrile inthe presence of hydrogen. Many of the new catalysts are soluble in, orform colloidal disperions in, the reaction medium. Suchcatalysts areundesirable for commercial operation since they present recoveryproblems. Further, it is desirable to enhance the yield of thesecatalysts to reduce the cost of the desired end-product, adiponitrile.

SUMMARY 'OETHE INVENTION The present invention comprises a process forthe production of organicdinitriles from acrylonitrile which comprisescontacting and reacting acrylonitrile with an atmosphere comprisinggaseous hydrogen at a pressure in the range between atmospheric pressureand 9000 p.s.i. and at a temperature in the range between about 80 C.and 175 C. in the presence of a catalytic amount of a catalystcomprising the reaction product, prepared in aqueous solution, of awater soluble ruthenium salt with a water soluble salt of an organicacid having a pK in aqueous solution, from 2.5 to 5.5, said reactionproduct being absorbed on a catalyst support of amorphous carbon oractivated 1 alumina, and recovering organic dinit-riles from thereaction product.

PREPARATION OF THE CATALYST The catalyst is prepared by reaction inaqueous solution of a water-soluble ruthenium salt and a water-solublesalt of a selected. organic acid. The preparation is preferablyconductedin the presence of the" support. Eifective catalysts can,however, be prepared by reacting the soluble components to form acomplex ruthenium-organic acid compound which is then adsorbed on thesupport.

3,655,724 Patented Apr. 11, 1972 The salts of ruthenium which can beemployed are those water-soluble halide salts of ruthenium inwhich thevalance of the ruthenium is +3 or +4 including simple salts whereinruthenium is the sole cation and complex salts in which the cationincludes ammonium or alkali metal cations, that is salts having theformula M RuX when M is an alkali metal or ammonium cation X is halogenand m is 3, or 4, and n is 0, 1, 2 or 3 when m is 3 and n=0 or 2 whenm=4. The coordination sphere may be completed with hydroxyl groups orwater of hydration. With certain salts of ruthenium, a mineral acid maybe needed to prevent hydrolysis to ill-defined insoluble basic salts. Inthat case, enough of the reacting salt of the organic acid must beemployed to react with the mineral acid as well as to provide a minimumof about 1 mole of organic acid per gram atom of ruthenium. Generally anexcess of the water-soluble salt of the organic acid is employed. Thiscan be sufiicient to provide 10 moles of the salt of the organic acidper gram atom of ruthenium.

The organic carboxylic acid, the salt of which is employed as the secondreactant, should have a pK of 2.5 to 5.5. Suitable acids include formicacid, acetic acid, chloroacetic acid, hydroxyacetic acid, diethylaceticacid, bromoacetic acid, propionic acid, u-bromopropionic acid, n-butyricacid, isobutyric acid, pivalic acid, n-caproic acid, n-caprylic acid,acrylic acid, crotonic acid, adipic acid, pimelic acid, maleic acid,fumaric acid, benzoic acid, 0-, mor p-toluic acids, 11- or ,B-napthoicacids, o-, mor p-chlorobenzoic acids, mor p-nitrobenzoic acids, andcinnamic acid.

Any salt of the above acids can be employed which is sufiiciently watersoluble. Suitable cations include ammonium, alkyl ammonium, or metalsfrom Groups Ia, I-Ia, Ib, Hb or VIII of the Periodic Table of theElements provided the selected salt is Water soluble.

The reaction between the ruthenium salt and the salt of the organic acidis conducted in aqueous solution. The proportions of the reactants arenot critical, provided that a sufiicient amount of the salt of theorganic acid is present to react with the ruthenium compound, i.e. about1 to about 10 gram moles of the salt of the organic acid per gram atomof ruthenium. The temperature at which the reaction is conducted islikewise not critical, but is preferably between about 50 C. and aboutC. to promote the reaction between the components and adsorption of thereaction product on the support.

The catalyst support is a critical feature of this invention. -It hasbeen found that the use of selected catalyst supports provides insolublecatalysts which are particularly adapted to use in continuous processesand in which the activity of the reaction product between solubleruthenium salts and the soluble salts of organic acids is enhanced. Thereaction products can be loosely called the ruthenium salts of theorganic acids, but are, in fact, basic compounds when prepared asdescribed hereinabove. The ruthenium salts of organic acids normally areactive catalysts, but the activity is substantially enhanced when thecompounds are adsorbed on the selected supports. The selected supportsare activated carbon, having a surface area preferably greater than 400m. /g. and '17 alumina. The amount of the support is chosen relative tothe proportions of the water soluble ruthenium salt and the watersolubleorganic acid salt to give a final concentration of from about 0.1 toabout 10% by weight of ruthenium, calculated as metal. The only efl ectof ruthenium concentration on the support appears to be on the rate ofreaction, higher concentrations of ruthenium giving higher rates ofreaction. The preferredconcentration for operatingmonvenience and.ready..-preparation f the catalyst isabout by weight. After adsorbingthe cataly t on the support, the catalyst can be. separated byfiltration, washed with water to re- EXAMPLES- 1-12 Examples 1-12demonstrate the use of supported catalysts prepared from aqueoussolutions of ruthenium tnchloride trihydrate andvarious carboxylic acidsalts in move surplusxsalts and dried in; air or invacuunL-The washingstep however is optional. k 5 the Presence Caliban; P i r the con ugateacldsof these saltsls 2.86.10 5,05. CATALYSTS FOR- DIMERIZATION v ,Thecatalysts were prepared bythe-follow'ngproce ure: ACRYLQN ITRILE Asolution of RuCl -3H O in ';0.6,-N HC'l (5,9 mg. The catalysts of thepresent invention can be used for lc r heat?d a .C' the dimerization ofacrylonitrile in the presence of hyfP t carbon q'wa surfed 1n; dl a q Qdrogen by contacting the reactants with a catalytic amount of the "saltas mdlcaled was added" wlth Wti at of a catalyst defined hereabove at'atemperature in the about e a Perlod- 51X minutes; The range betweenabout 80 C. to about 175 C., preferably Suspenslon surfed and heated 5.1 for 0 0 c, at a pressure between atmospheric pressure If hour, afterwhich 1t was cooled to room'temperature and and 9000 p,s,i preferably f100 to 50.0 i 0 filtered. The solids were washed on the filter with dis-The reaction can be conducted in the presence of a tilled Water Untilthe w in W free 9 chlciridfi i011- solvent inert to the reactants andproducts, such as ali- The catalyst was thehrdlied at room temperaturein the phatic and aromatic hydrocarbons and halohydrocarbons, p n airfor minutes and under reduced pressu e v ralcohols, ethers, nitriles,amides and phosphoramides. Solg 1 I p vents, however, are not necessaryin the process of this The C ysts included in Ta l d" W tested bytheinvention and are not preferred, since it is necessary to f llowingprocedure: A mixture of 0.2g. of- -the..catalyst separate the'productsfrom the solvent. and 20 ml. (16 g.) of acrylonitrile, iIlz-ZlStfllIllBSS steel The process of the present invention can be conductedpressure vessel was agitated and heated at 125 C. under in a batchprocess or, alternatively and for commercial 200 lb./sq. in.hydrogenpressure' for 12 hours. The presoperation preferably, thereaction can be conducted consure was maintained by repressuring fromtime to time TABLE I Yield of Conversion t Ca'linear of acrylo-RuCh-ISHzO pKa of dinitrile nitrile Example (g.) Precipitant solutionSupport acid ,(percent) I I (percent) a 1. 16 38 ml. 10% ammoniumacetate Powdered carbon- 4. 76 65. 2 94. 5 1. 16 do Granular carbon 4.76 54. 8 95. 2 0.58 19 ml. 10% ammonium acetate--- .do.' 4.76 55.4 42.22. 32 76 ml. 10% ammonium acetate--- 4. 76 52.8 99. 9 1.16 40 ml. 10%sodium acetate 4. 76 57. 2 58. 2 1.16 ml. 10% ammonium formate 3.75 56.731.0 1. 16 47 ml. 10% ammonium chloroaoetate 2. 86 58. 8 48. 3 1. 16 48ml. 10% potassium acetate 4. 76 55. 7 83. 0 1.16 50 ml. 20% magnesiumacetate tetrahydrate 4. 76 53. 5 97. 9 1. 16 4.3 g. of ammoniumhydroxyacetate in m1. of Wate do 3. 82 57. 3 68. 9 1. 16 11.56 g.eobaltous acetate tetrahydrate in ml. of water do 4. 76 60. 3 96. 4 1.16 5.5 g. ammonium pivalate in 251111. of water Powdered carbo'm. 5. 0551. 3 99. 9

a Ca linear dinitriles are the total of cisandtrans-1,4-dicyano-1-butene and adiponitrile in the liquid product. Yieldis based onexpended (unrecovered) acrylonitrile.

b The preparation of catalyst in this instance involved fluid. Also thewet solid was divided into two portions, washed catalyst.

e Catalysts from 1.16 g. RuOl -3Hz0 contain about 5% or loss Ru on thesupport.

d Granular carbon was 6-14 mesh charcoal.

' The dimerization test was made with 0.5 g. of catalyst.

tinuously by passing acrylonitrile and hydrogen at the above-describedtemperature and pressure over a bed of .the catalyst. After passing theacrylonitrile in an atmosphere of hydrogen over the catalyst bed, theproduct dinitriles (adiponitrile, cisand trans-1,4-dieyano-l-butene) areseparated; the unchanged acrylonitrile is recovered and recycled; andthe propionitrile formed as a by-prodnot by hydrogenation of theacrylonitrile is also recovered, dehydrogenated to acrylonitrile byknown procedures such as that taught in US. Pat. 2,554,482, and in theform of acrylonitrile is returned to the'recycle stream. I

This invention is further illustrated by the following examples in whichparts are given by-weight unless otherwise stated. It is to beunderstood,-however, that these examples arenot intended to fullydelineate the scope preparation and testing use of 15 ml. of 0.8 N HClinitially and later addition of 15-20 ml. of water to keep the mixtureonly one of which was washed free of chloride ion. The demirization testwas made with the Ru (as organic acid derivative). Other amounts ofRuCh'3H O give proportionately more,

tiNHo'aR lu o with ammonium acetate, and sodium benzoate, respectively,;on granular carbon. The general procedures for catalyst are. the same asfor Examples of this discovery. 1'-12- TABLE 1r Yield of- Conversion apKBof Cflinear of acryl- (NHOZRHCIQ conjugate dinitriles' onitrileExample (g.) Precipitant solution acid (percent),v (percent) b 1. 47 38ml 10% ammonium acetate 4. 76 as. 5 9-5 4. 20 56.3 78.7

' 1.47 30.1111. H O cQntaining 6.62 g. sodium benzoate a The wetcatalyst was washed with ml. of 10% aqueous ammonium acetate andthen'succeSsiVeIy withthree 50-1111. portions of distilled water.

* This amount of Nn'mauol g gives catalyst containing about 5% Ru asacetate derivative) on the sup ort.

EXAMPLES -16 Examples 15 and 16 demonstrate the use of a catalystcontaining 5% Ru (as acetate derivative) on n-alumina and the eifect oftemperature in the dimerization. The catalyst was prepared by the methoddescribed for the carbon-supported catalysts of Examples 1-12, using1.16 g, of 'RuCl -3H O, 38 ml. of 10% ammonium acetate, and 9.0 g. ofpowdered -Al O However, the procedure was altered somewhat in thatintroduction of the alumina to the mixture was withheld until sufficientammonium acetate had been added to give a pH of 2.7, and the wetcatalyst was washed with 120 ml. of 5% ammonium acetate prior to thewashing with distilled water.

In the dimerization test, the amount of supported catalyst and thetemperature were varied, as indicated in Table III.

TABLE III Yield of Conversion Ct linear of acrylo- Weight ofTemperadinitriles mtrlle Example catalyst (g.) ture C.) (percent)(percent) EXAMPLES 17-26 (TABLE IV) TABLE IV Yield of Conversion Cslinear of acrylodinitriles nitrile E xample Solvent (percent) (percent)17 e Hexamethylphosphoramlde- 49. 3 38. 3 18 b ..d0 61.9 31. 5 19-.-.-.do 57.2 66.8 20 Dlmethylacetamid 48. 8 95. 7 21 Dimethylfonnarnlde.51. 0 100 22 Absolute ethanoL. 51. 8 100 23 n-Butanol 55. 1 99. 8 242-methoxyethanol. 56. 8 09. 8 25 Acetonltrile 50. 1 100 26 Toluene 53. 7100 B The test procedure involved use of 1.0 g. of the catalyst ofExample 1,

40 ml. of solvent, 11.2 g. of aerylonitrlle, and 40 lb./sq. in. hydrogenpressure. The heating time was 16% hours.

b 0.2 g. of catalyst was used.

EXAMPLES 27-28 Examples 27 and 28 demonstrate the influence of acatalyst support on the relative proportions of dicyanobutene andadiponitrile in the C linear dinitrile portion of the product. The testprocedure of Examples 1-12 was a Each catalyst contained about 0.05 g.of ruthenium. b No support or precipitant.

EXAMPLES 29-31 Examples 29-31 demonstrate the effects of certainvariations in the preparation of insoluble unsupported andcarbon-supported catalysts based on RuCl -3H O and ammonium acetate. Theprimary colloidal rutheniumcontaining suspension was prepared by adding40 ml. of 10% aqueous ammonium acetate dropwise to a solution of 1.16 g.RuCl -3H O in 20 ml. of 0.6 N HCl. The test procedure follows thatdescribed for Examples 1-12.

In Example 30, the primary colloid was neutralized with sodium carbonateto obtain a neutral unsupported catalyst which would be closelycomparable in neutrality to a water-washed supported catalyst.Otherwise, the presence of sodium carbonate is immaterial in thedimerization test.

a It can be shown that the catalytic activity of a supported catalyst isnot diminished by adding water to the test mixture.

b The catalyst was obtained by adding 9.0 g. of powdered charcoal to theprimary colloid and thereafter following the procedure of Examples 1-12(or catalyst preparation.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A method of dimerizing acrylonitrile to linear dinitriles whichcomprises contacting and reacting acrylonitrile in the presence ofhydrogen at a pressure between atmospheric pressure and 9000 psi, and ata temperature in the range between about C. and 175 C. with a catalyticamount of a catalyst consisting essentially of amorphous carbon or-alumina having adsorbed thereon the reaction product, in aqueoussolution, of a Water soluble ruthenium salt and a water soluble salt ofan organic acid, said organic acid having a pk measured in aqueoussolution of from 2.5 to 5.5.

2. The process of claim 1 in which said water soluble salt of an organicacid is ammonium acetate, sodium acetate, potassium acetate, magnesiumacetate, cobalt acetate, ammonium formate, ammonium chloroacetate,ammonium pivalate, ammonium hydroxyacetate or sodium benzoate.

3. The process of claim 2 in which the water soluble ruthenium salt hasthe formula wherein M is an alkali metal cation or ammonium cation, X ishalogen, m is 3 or 4 and n is 0, 1, 2 or 3 when m is 3 and n is 0 or 2when m is 4.

4. The. process of claim 3 in which said reaction product is formed inthe presence of said amorphous carbon or said 1 alumina.

5. The process of claim 4 in which the reaction product is formed at atemperature of about 50 C. to about C.

6. The process of claim 5 in which the pressure is from to 500 p.s.i.

References Cited UNITED STATES PATENTS 3,013,066 12/1961 Alderson260465.8D

JOSEPH P. BRUST, Primary Examiner

